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Atomic size is the distance between the centre of an atom to the outermost shell, in other words it is the radius of the atom.

The phenomenon due to which the vibrations of light are restricted in a particular plane is called the polarisation of light.

The combining power or the combining capacity of an element is called its valency. The number of atoms of other elements with which one atom of an element combines is decided by the valency of that element.

The electron affinity of an element is the energy given off when a neutral atom in the gas phase gains an extra electron to form a negatively charged ion.